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PubMed2002

Spatial distribution of leaf morphological and physiological characteristics in relation to local radiation regime within the canopies of 3-year-old Populus clones in coppice culture.

Spatial distributions of leaf characteristics relevant to photosynthesis were compared within high-density coppice canopies of Populus spp. of contrasting genetic origin. We studied three clones representative of the range in growth potential, leaf morphology, coppice and canopy structure: Clone Hoogvorst (Hoo) (Populus trichocarpa Torr. & Gray x Populus deltoides Bartr. & Marsh), Clone Fritzi Pauley (Fri) (Populus trichocarpa Torr. & Gray) and Clone Wolterson (Wol) (Populus nigra L.). Leaf area index ranged from 2.7 (Fri and Wol) to 3.8 (Hoo). The clones exhibited large vertical variation in leaf area density (0.02-1.42 m2 m-3). Leaf dry mass per unit leaf area (DM(A)) increased with increasing light in Clones Hoo and Fri, from about 56 g m-2 at the bottom of the canopy to 162 g m-2 at the top. In Clone Wol, DM(A) varied only from 65 to 100 g m-2, with no consistent relationship with respect to light. Conversely, nitrogen concentration on a mass basis was nearly constant (around 1.3-2.1%) within the canopies of Clones Hoo and Fri, but increased strongly with light in Clone Wol, from 1.4% at the bottom of the canopy to 4.1% at the top. As a result, nitrogen per unit leaf area (N(A)) increased with light in the canopies of all clones, from 0.9 g m-2 at the bottom to 2.9 g m-2 at the top. Although a single linear relationship described the dependence of maximum carboxylation rate (17-93 micromol CO2 m-2 s-1) or electron transport capacity (45-186 micromol electrons m-2 s-1) on N(A), for all clones, Clone Wol differed from Clones Hoo and Fri by exhibiting a higher dark respiration rate at low N(A) (1.8 versus 0.8 micromol CO2 m-2 s-1).

Carbon↗
PubMed2002

Clustering instability of the spatial distribution of inertial particles in turbulent flows.

A theory of clustering of inertial particles advected by a turbulent velocity field caused by an instability of their spatial distribution is suggested. The reason for the clustering instability is a combined effect of the particles inertia and a finite correlation time of the velocity field. The crucial parameter for the clustering instability is the size of the particles. The critical size is estimated for a strong clustering (with a finite fraction of particles in clusters) associated with the growth of the mean absolute value of the particles number density and for a weak clustering associated with the growth of the second and higher moments. A new concept of compressibility of the turbulent diffusion tensor caused by a finite correlation time of an incompressible velocity field is introduced. In this model of the velocity field, the field of Lagrangian trajectories is not divergence free. A mechanism of saturation of the clustering instability associated with the particles collisions in the clusters is suggested. Applications of the analyzed effects to the dynamics of droplets in the turbulent atmosphere are discussed. An estimated nonlinear level of the saturation of the droplets number density in clouds exceeds by the orders of magnitude their mean number density. The critical size of cloud droplets required for cluster formation is more than 20 microm.

Journal Article↗
PubMed2000

Changes in the kinetics of dopamine release and uptake have differential effects on the spatial distribution of extracellular dopamine concentration in rat striatum.

The objective of this study was to examine whether the limited diffusion distance of dopamine in rat striatum produces spatial heterogeneity in the extracellular dopamine concentration on a dimensional scale of a few micrometers. Such heterogeneity would be significant because it would imply that the concentration of dopamine at a given receptor depends on the receptor's ultrastructural location. Spatially resolved measurements of extracellular dopamine were performed in the striatum of chloral hydrate-anesthetized rats with carbon fiber microdisk electrodes. Dopamine was monitored during electrical stimulation of the nigrostriatal pathway before and after administration of drugs that selectively affect the kinetics of evoked dopamine release and dopamine uptake. The effects of nomifensine (20 mg/kg), L-DOPA (250 mg/kg), and alpha-methyl-p-tyrosine (250 mg/kg) on the amplitude of the stimulation responses were examined. The outcome of these experiments was compared with predictions derived from a mathematical model that combines diffusion with the kinetics of release and uptake. The results demonstrate that the extracellular dopamine concentration is spatially heterogeneous on a micrometer scale and that changing the kinetics of dopamine release and uptake has different effects on this spatial distribution. The impact of these results on brain neurochemistry is considered.

Animals↗
PubMed2000

Spatial distributions of expansion rate, cell division rate and cell size in maize leaves: a synthesis of the effects of soil water status, evaporative demand and temperature.

The spatial distributions of leaf expansion rate, cell division rate and cell size was examined under contrasting soil water conditions, evaporative demands and temperatures in a series of experiments carried out in either constant or naturally fluctuating conditions. They were examined in the epidermis and all leaf tissues. (1) Meristem temperature affected relative elongation rate by a constant ratio at all positions in the leaf. If expressed per unit thermal time, the distribution of relative expansion rate was independent of temperature and was similar in all experiments with low evaporative demand and no water deficit. This provides a reference distribution, characteristic of the studied genotype, to which any distribution in stressed plants can be compared. (2) Evaporative demand and soil water deficit affected independently the distribution of relative elongation rate and had near-additive effects. For a given stress, a nearly constant difference was observed, at all positions of the leaf, between the relative elongation rates of stressed plants and those of control plants. This caused a reduction in the length of the zone with tissue elongation. (3) Methods for calculating cell division rate in the epidermis and in all leaf tissues are proposed and discussed. In control plants, the zone with cell division was 30 mm and 60 mm long in the epidermis and in whole tissues, respectively. Both this length and relative division rate were reduced by soil water deficit. The size of epidermal and of mesophyll cells was nearly unaffected in the leaf zone with both cell division and tissue expansion, suggesting that water deficit affects tissue expansion rate and cell division rate to the same extent. Conversely, cell size of epidermis and mesophyll were reduced by water deficit in mature parts of the leaf.

Cell Division↗
PubMed2003

Spatial distribution of human respiratory system transfer impedance.

Transfer impedance (Ztr) of the respiratory system provides specific information on airways and tissues, but little is known about its spatial distribution in the different thoracoabdominal regions. To study Ztr distribution on the chest wall surface we analyzed five healthy subjects in the supine position by applying a sinusoidal forcing pressure (4, 8, and 12 Hz) at the mouth and measuring airway opening pressure and flow. Three-dimensional positions of 68 reflective markers placed on the chest wall over selected reference points were simultaneously measured by an optoelectronic motion analyzer. A subset of ten points placed on the midline were used to measure chest wall movements in the craniocaudal direction. While the motion of rib cage markers was synchronous, the abdominal markers demonstrated surface waves propagating caudally. The amplitude and phase of these waves were strongly dependent on position and frequency. We used a new method to measure total and local chest wall volume variations to compute the distribution of Ztr over the chest wall. Above 4 Hz we found that Ztr was inhomogeneously distributed and strongly dependent on position and frequency, mainly in the abdomen where the phase was often more more than 180 degrees with high values of modulus. For this reason, we conclude that above 8 Hz Ztr represents rib cage mechanics almost exclusively.

Abdomen↗
PubMed2000

Spatial distribution of GC- and AT-rich DNA sequences within human chromosome territories.

Previous topological analyses of DNA sequence organization in the interphase chromosome mainly focused on the spatial distribution of individual gene copies within chromosome territories. In order to achieve a more comprehensive view into the subchromosomal arrangement of DNA, we isolated the GC-richest/gene-richest fraction (H3 isochores) as well as AT-richest/gene-poorest fraction of human genomic DNA (L1+L2 isochores) and visualized the respective DNA within individual chromosome territories by means of dual-color FISH. Application of confocal laser scanning microscopy and dedicated 3D image analysis software, which differentiated territory subvolumes by peeling shells one voxel in width, revealed a significant difference in the intraterritorial distribution of these two DNA sequence classes. While the H3 isochores were found localized in all subvolumes of the territories at similar frequency, simultaneously detected L1+L2 isochores were observed more to the interior of the same chromosome territories. Thus the GC-rich sequences display a much higher variability in their intraterritorial localization than AT-rich DNA fragments.

Chromosomes, Human↗
PubMed1995

Semi-automatic data acquisition for quantitative neuroanatomy. MicroTrace--computer programme for recording of the spatial distribution of neuronal populations.

We present a computer programme, MicroTrace, designed for user-guided digitisation of objects in biological sections. The programme is optimised for recording the spatial distribution of neuronal structures, such as large populations of tracer-labelled cell bodies or axonal plexuses, regional borders, and surfaces. System requirements are a PC running Microsoft Windows, a microscope equipped with stepping motors, and a drawing tube. A computer generated drawing area, surrounded by menus and icons, is projected into the microscope field of view via the drawing tube. Different 'object' icons are assigned to individual object categories (cell types, surfaces, etc.). Digitisation is performed by pointing the cursor at objects in the section. Computer graphical symbols are superimposed on the digitised objects. All object categories are digitised, before moving the stage to other fields of view by manipulating the joystick or scroll bars. Movement of the microscope stage is accompanied by a translation of the graphical image, so that continuous feedback on the progress of the digitisation is provided. MicroTrace can readily be adapted to the specific needs of the user. We show its use in different experimental neuroanatomical techniques. Two-dimensional images and three-dimensional reconstructions of neuronal distribution and surfaces are demonstrated.

Animals↗
PubMed1976

Quantitation of the spatial distribution of 'prespore vacuoles' in pseudoplasmodia of Dictyostelium discoideum.

The axial distribution of an organelle, the prespore vacuole (PV), previously reported absent from the prestalk region, was determined in pseudoplasmodia of varying sizes, under differing conditions of photostimulation of migration. The distribution of these organelles, determined quantitatively by electron microscopy of sections from known axial locations, was found to have a spatial pattern which varied with pseudoplasmodial size. The total complement of these organelles appeared constant for any size of pseudoplasmodium under similar conditions of illumination. Increased illumination decreased the total number of the organelles. The spatial distribution of PV varies with total cell number, and the size of the region with no PV bears no relationship to the proportion of the cell mass which would form stalk cells. Similarly, the number of cells containing PV bears no fixed relationship to the number of cells which will form spores. On these grounds, the reported role of PV, that of directing or reflecting spore differentiation, appears unlikely.

Cell Differentiation↗
PubMed1986

Studies of the temporal and spatial distribution of aerosols in multi-tiered inhalation exposure chambers.

Two multi-tiered whole body inhalation exposure chambers with nominal volumes of 1 m3 (H-1000) and 2 m3 (H-2000) were evaluated for their performance in terms of the temporal and spatial distribution of test aerosols within the chamber. Parameters investigated included chamber type, single-chamber-single-aerosol generator versus two-chamber-single-aerosol generator systems, chamber air supply and exhaust systems, particle size, and aerosol diluter type. Results indicated that: 1) particle size has an effect on chamber aerosol concentration distribution, with the larger particle resulting in a higher variation; 2) the single-chamber-single-generator system is more stable than the two-chamber-single-generator system; 3) the H-2000 chamber has a lower aerosol spatial variability than the H-1000 chamber; and 4) the aerosol distribution within the chamber could be improved with the use of a newly designed diluter.

Aerosols↗
PubMed1997

Spatial distribution of postotic crest cells defines the head/trunk interface of the vertebrate body: embryological interpretation of peripheral nerve morphology and evolution of the vertebrate head.

The migration pathways and spatial distribution of neural crest cells largely depend on the embryonic architecture. At the preotic level in the chick embryo, cephalic crest adhere to even-numbered rhombomeres proximally, and populate each pharyngeal arch distally, thus prefiguring the morphology of the branchiomeric nerves. This distribution pattern is possible because of the absence of somites in the head. In the postotic region, however, somites and pharyngeal arches coexist at the same axial level. The caudalmost cephalic crest cell population, the circumpharyngeal crest cells, are derived from the postotic crest and their distribution covers the entire innervation areas of cranial nerves IX and X. In their proximal migration pathway, circumpharyngeal crest cells can exist along the dorsolateral pathway only where somites are absent. They divert around the occipital somites rostrally, making an arc that represents the caudal limit of the dorsolateral pathway of cephalic crest cells, or the head/trunk interface at the paraxial level. Ventrally, the circumpharyngeal crest cells localize in postotic pharyngeal arches as well as in an arc-shaped ridge, called the circumpharyngeal ridge. Since the circumpharyngeal ridge represents the caudal limit of the pharynx, it indicates the head/trunk interface at the level of the lateral body wall. These two interfaces of reverse orientation make an S-shaped, head/trunk interface together. Several structures unique to this region develop in this interface. Since the rhombomeric compartmentalization is distinct only in higher vertebrates, the rhombomere-dependent segregation of cephalic crest cells is more likely to be a secondary feature of the vertebrate head. The topographical configuration of the vertebrate crest cell distribution pattern does not support the idea that the vertebrate head evolved as a specialized trunk. but rather supports the idea that two distinct methods of segmental patterning have evolved in rostral and caudal parts of the vertebrate body, which resulted in the head and trunk, respectively. Postotic crest is located at the intermediate level between the trunk and the head, giving rise to both the cephalic and trunk crest cells. Its cephalic components circumpharyngeal crest cells, are distributed only rostral to the S-shaped interface.

Animals↗
PubMed2001

Spatial distribution of cingulate cells projecting to the primary, supplementary, and pre-supplementary motor areas: a retrograde multiple labeling study in the macaque monkey.

We examined the location and spatial distribution of cingulate cortical cells projecting to the forelimb areas of the primary motor cortex (MI), supplementary motor area (SMA), and pre-supplementary motor area (pre-SMA) using a multiple retrograde labeling technique in the monkeys (Macaca fuscata). The forelimb areas of the MI, SMA and pre-SMA were physiologically identified, based on the findings of intracortical microstimulation (ICMS) and single cell recording. Three different tracers, diamidino yellow (DY), fast blue (FB), and wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP), were injected into each of the three motor areas in the same monkey. Retrogradely labeled cells in the cingulate cortex were plotted with an automated plotting system. Cells projecting to the forelimb area of the MI were distributed in the two separate regions situated rostrocaudally in the dorsal and ventral banks of the cingulate sulcus, namely the rostral cingulate motor area (CMAr) and caudal cingulate motor area (CMAc). These two regions corresponded to the forelimb areas identified by the ICMS in the same animal. The distribution of projection cells to the SMA overlapped extensively with that of projection cells to the MI. Although the MI received relatively sparse inputs from the CMAr than from the CMAc, the SMA received inputs from the CMAr and its adjacent areas as much as from the CMAc. The projection cells to the pre-SMA were distributed in the anterior portion of the cingulate cortex, including the anterior part of the CMAr and in a small part of the cingulate gyrus. These findings indicate that the MI and SMA share a considerable common information from the cingulate cortex, including the CMAr and CMAc, whereas the pre-SMA receives a different set of information from the anterior part of the cingulate cortex.

Animals↗
PubMed2003

Imaging the spatial distribution of transgene expression in the lungs with positron emission tomography.

This study was designed to evaluate the utility of positron emission tomography (PET) to quantify the magnitude and spatial distribution of transgene expression after different methods of adenoviral vector delivery (with surfactant- and saline-based vehicles) within rat lungs. In all, 17 animals (eight in the surfactant group, nine in the saline group) were studied 3 days after intratracheal administration of a replication-incompetent adenovirus encoding a mutant Herpes simplex virus-1 thymidine kinase (mHSV1-TK)-enhanced green fluorescent protein fusion gene driven by a Cytomegalovirus promoter (Ad-CMV-mNLS-HSV1sr39tk-egfp). PET images were obtained 1 h after i.v. administration of 9-(4-[(18)F]-fluoro-3-hydroxymethylbutyl)guanine ([(18)F]-FHBG), an imaging substrate for mHSV1-TK. Overall, the average lung concentration of [(18)F]-FHBG was significantly greater in the surfactant group than in the saline group (0.24+/-0.06 versus 0.17+/-0.03% injected dose/ml lung, P< or =0.05). Lung [(18)F]-FHBG distribution was more peripheral and more homogeneous in the surfactant group than in the saline group (mean coefficient of variation=31+/-4 versus 36+/-3%, respectively, P< or =0.05). Regions of increased tracer concentration in the surfactant group compared to the saline group were evenly distributed throughout the lungs. We conclude that PET imaging provides useful and meaningful information about the effectiveness of different gene transfer delivery strategies within the lungs, and that surfactant-based vehicles may be a superior strategy for pulmonary gene transfer.

Adenoviruses, Human↗
PubMed1971

Prediction of the spatial distribution of cell survival in heavy ion beams.

The possible use of heavy ion beams for biomedical applications was examined through calculations of the physical beam properties and the spatial distribution of cell survival. Range straggling, creation of secondary particles, electron pickup, and the effects of inhomogeneous absorbers were analyzed in terms of cell survival. Depth-survival plots for typical irradiations provide substantial encouragement for the investigation of these beams for biomedical applications in which localized tissue destruction is desired.

Cell Survival↗
PubMed2000

Difference spatial distribution function analysis of aqueous solutions. IV. Hydration structure changes of ethylene glycol solutions throughout conformational change process from gGg' to tGg' conformers.

Monte Carlo (MC) simulations were carried out for an infinitely dilute aqueous solution of two stable conformers (gGg' and tGg') and of three conformations between gGg' and tGg' conformers of ethylene glycol (EG) at 298K. Based on the spatial distribution function (SDF) goo(x,y,z), obtained from the MC simulation in the above conformations in liquid water, the high distribution of hydration water molecules could be divided into hydrogen acceptor (HA), hydrogen donor (HD), MIX (overlapped distribution of HA and HD), and hydrophobic hydration (HH) regions. The spatial orientations of hydrogen-bonded water molecules were found to be of a linear type with a triple-layer structure in the HA region and HA part (in the MIX region), and double-layer structures in the HD region and HD part (in the MIX region). In addition, it was apparent that the spatial orientations of these water molecules were of the linear type throughout the conformational change process from gGg' to tGg' conformers in liquid water. From the difference SDF (DSDF), deltagoo(x,y, z), between the SDFs of two conformations, we concluded that the distribution of hydration water molecules in the HA and HD parts of the MIX region are governed by the competition of internal hydrogen bonds between the hydrogen atom and two lone-pair electrons on the oxygen atom of an EG molecule.

Algorithms↗
PubMed1991

Spatial distribution of "tissue-specific" antigens in the developing human heart and skeletal muscle. II. An immunohistochemical analysis of myosin heavy chain isoform expression patterns in the embryonic heart.

The spatial distribution of alpha- and beta-myosin heavy chain isoforms (MHCs) was investigated immunohistochemically in the embryonic human heart between the 4th and the 8th week of development. The development of the overall MHC isoform expression pattern can be outlined as follows: (1) In all stages examined, beta-MHC is the predominant isoform in the ventricles and outflow tract (OFT), while alpha-MHC is the main isoform in the atria. In addition, alpha-MHC is also expressed in the ventricles at stage 14 and in the OFT from stage 14 to stage 19. This expression pattern is very reminiscent of that found in chicken and rat. (2) In the early embryonic stages the entire atrioventricular canal (AVC) wall expresses alpha-MHC whereas only the lower part expresses beta-MHC. The separation of atria and ventricles by the fibrous annulus takes place at the ventricular margin of the AVC wall. Hence, the beta-MHC expressing part of the AVC wall, including the right atrioventricular ring bundle, is eventually incorporated in the atria. (3) In the late embryonic stages (approx. 8 weeks of development) areas of alpha-MHC reappear in the ventricular myocardium, in particular in the subendocardial region at the top of the interventricular septum. These coexpressing cells are topographically related to the developing ventricular conduction system. (4) In the sinoatrial junction of all hearts examined alpha- and beta-MHC coexpressing cells are observed. In the older stages these cells are characteristically localized at the periphery of the SA node.

Adult↗
PubMed2002

Spatial distribution patterns of interphase centromeres during retinoic acid-induced differentiation of promyelocytic leukemia cells.

BACKGROUND: The pericentromeric heterochromatin is an important element for the regulation of gene silencing. Its spatial distribution during interphase appears to be cell-type specific. This study analyzes three-dimensional (3D) centromere distribution patterns during cellular differentiation along the neutrophil pathway. METHODS: Differentiation of the promyelocytic leukemia cell line NB4 was induced by retinoic acid. Centromeres in interphase nuclei were visualized by immunofluorescence staining of centromere-associated proteins with CREST serum. 3D images of nuclei were obtained by confocal microscopy. Automated methods for the segmentation of point-like objects in 3D images were implemented to detect the position of centromeres. Features of centromere localization patterns were determined by constructing the minimal spanning tree of the centromere distribution. RESULTS: In differentiated NB4 cells, the number of centromere conglomerates (chromocenters) was decreased and the distance between chromocenters was increased as compared with untreated controls. The nuclear volume did not differ between the two groups. CONCLUSIONS: The measured rearrangement of centromeres indicates a progressive clustering of heterochromatin and a global remodeling of interphase chromosome territories during differentiation of NB4 cells. The developed methods for the analysis of 3D centromere distribution patterns provide the opportunity for a fast and objective analysis of heterochromatin remodeling.

Algorithms↗
PubMed1992

Spatial distribution of the Sm antigen in Drosophila early embryos.

Anti-Sm antibodies recognize the major small nuclear RNA-protein particles (snRNPs) involved in pre-mRNA processing. The spatial distribution of the snRNPs has been investigated in Drosophila embryos up to the cellularization stage (cycle 14), using the Y12 anti-Sm antibody. Our results show that: 1) all or most of the Sm antigen is localized in the cytoplasm of the syncytial blastoderm until the 12th cycle of division, in both the nuclear and cytoplasmic compartments at cycle 13, and then in the nuclei at cycle 14 and later. This relocalization takes place when zygotic transcriptional activation occurs; 2) at the subcellular level, the Sm antigen localizes in a speckled pattern and in foci-like structures within the nucleus of Drosophila blastoderm embryos; 3) strikingly, some nuclei of embryos at the 14th cycle appear to contain more snRNPs than others. The position of these nuclei differs from one embryo to another, and their distribution does not resemble any known developmental pattern of Drosophila embryogenesis. We propose that random differences in snRNP concentration may serve as an epigenetic signal for stochastic events occurring during development.

Animals↗
PubMed2003

Temporal and spatial distribution of paramoebae in the water column--a pilot study.

Amoebic gill disease is the main disease affecting the salmonid industry in Tasmania, but no information on the distribution of the causative pathogen, Neoparamoeba pemaquidensis, in the aquatic environment is available. This pilot study aimed to determine temporal and spatial distributions of paramoebae species in the water column, using an immuno-dot blot technique. Water samples were collected from inside fish cages at various depths (0.5, 5.5 and 11.0 m) in both summer and winter, as well as various distances (0, 0.5, 240, 280, 750 and 1100 m) away from the sea cage and farming site. Paramoebae densities were estimated using the most probable number technique (MPN). Temperature, salinity, dissolved oxygen, turbidity, nitrite and nitrates, and bacterial counts were measured for each water sample. Data were analysed using a residual maximum likelihood test and significant associations between paramoebae densities and environmental factors were analysed. Results showed that densities were significantly higher in summer (P = 0.017), at 5.5 m depth (P = 0.029), and reduced to the lowest density at 1100 m away from the cage sites (P = 0.008). Bacterial counts, turbidity and temperature were found to be significantly associated with paramoebae densities.

Amoebida↗